Environmental Engineering Reference
In-Depth Information
However, they emit a much lower amount of thermal radiation. Materials for selec-
tive coatings can no longer simply be painted or sprayed onto a surface. More
complicated coating methods are now necessary.
Figure 6.5 Principle of selective absorbers.
6.2.3 Air-Based Collectors
In most cases, solar collectors heat water. However, air and not water should be
used to heat the air of rooms. With conventional heating systems, radiators or
heating pipes installed under the fl oor transfer the heat produced from hot water to
the air. Instead of water, air can also be transmitted by a solar collector.
As air absorbs heat considerably less effectively than water, much larger absorber
cross-sections are required. Otherwise, in principle, air-based collectors differ very
little from liquid - based fl at-plate collectors. Figure 6.6 illustrates an air-based col-
lector with perforated absorbers. An integrated photovoltaic module can deliver the
solar safety glass
photovoltaic cells
absorber ribs
intake opening
outlet tube
Figure 6.6 Cross-section of an air-based collector. Illustration: Grammer Solar GmbH.
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